Modular capillary pumped loop cooling system

ABSTRACT

A modular capillary pump loop (CPL) cooling system and associated components. The modular CPL cooling system transfers heat from high-power circuit components, such as microprocessors disposed within computer chassis, to other locations within or external to the chassis, where the heat can be more easily removed. In various embodiments, the CPL cooling system includes one or more evaporators connected to one or more condensers via flexible liquid transport and vapor transport lines. A wicking structure, such as a volume of sintered copper, is disposed within each condenser. The wicking structure draws working fluid (e.g., water) in a liquid state into the evaporator based on a capillary mechanism and a pressure differential across a meniscus/vapor interface on an upper surface of the wicking structure. As the liquid meniscus is evaporated, additional fluid is drawn into the evaporator. The working fluid is then condensed back into a liquid in the condenser.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.09/957,792, filed 20 Sep. 2001, and claims priority therefrom under 35U.S.C. §120. The priority application is now issued U.S. Pat. No.6,981,543.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention concerns cooling systems for computer systems ingeneral, and capillary pumped loop cooling systems and componentsadapted for high-density computer servers in particular.

2. Background Information

Recent market demands have led the computer industry to develop computersystems with increased circuit densities. For example, many hardwarevendors, such as Intel, Hewlett-Packard, IBM, Compaq, and Dell, offerhigh-density rack-mounted servers that enable a large number of serversto be housed within a single standardized rack. The chassis for theserack-mounted servers are configured to have a specific form factor thatis designed to the standardized rack the servers are to be installed in.In one configuration, an ultra-thin form factor, known as the “1U” formfactor, is used. Under the 1U form factor, the chassis height for eachserver is only 1.75 inches. In another configuration, known as the “2U”form factor, the chassis height for each server is 3.5 inches.

In addition to increased circuit density, the components in thesecomputer servers are operating at higher and higher frequencies. Forexample, recent microprocessor clock rates typically exceed 1.5gigahertz. As a result, these components, especially microprocessors,generate a large amount of heat, which must be removed from the chassisso that the components do not overheat. In conventional computersystems, this heat is generally removed using forced air convection,which transfers the heat from the heat-producing circuit components byusing one or more “muffin” fans that are disposed within or coupled tothe chassis to draw air over the components through the chassis. Inaddition, heat sinks are often mounted to various high-power circuitcomponents, such as CPUs, to enhance natural and forced convection heattransfer processes.

In general, the rate at which heat is removed from a component is afunction of the component's surface area and the velocity of the airflowing over that surface area, coupled with the temperaturedifferential between the component surface and the air. Oftentimes, heatsinks are mounted on high temperature components to assist in removingheat from these components. For example, heat sinks comprising an arrayof fingers having a height of approximately 1-2 inches are commonly usedto cool microprocessors in desktop systems, workstations, andpedestal-mounted servers. The heat sinks provide significantly greatersurface areas than the components they are mounted to.

The low profiles of the 1U and 2U form factors create several problemsfor thermal engineers. Due to internal height limitations and airflowconsiderations, the use of heat sinks is generally restricted to lowerprofile heat sinks, which are much less efficient than the taller heatsinks discussed above. Also, in order to provide sufficient cooling viaforced air convection, there needs to be adequate airflow passages.Although heat sinks are advantageous in many instances, they createsignificant airflow restrictions that greatly reduce the velocity ofairflow through a computer chassis. They also take up space that may beused by other system components. Additionally, since the area of a fanblade is roughly proportional to the amount of airflow generated by amuffin fan (when fans having different diameters are rotated at the samespeed), the smaller fans used in 1U and 2U form factors draw less airthat the larger fans found in computer system chassis having larger formfactors. As a result, the use of heat sinks in multiple microprocessor1U configurations may be prohibited entirely. In other cases, it isnecessary that the multiple processors be aligned to provide adequateairflow over all of the microprocessors, which may limit the circuitdesign.

To address the foregoing problems, thermal cooling systems incorporatinga large planar heat pipe have been proposed for transporting the energyto another location in a 1U chassis where the energy may be more easilydissipated.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisinvention will become more readily appreciated as the same becomesbetter understood by reference to the following detailed description,when taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic diagram illustrating a conventional capillarypumped loop (CPL) cooling system;

FIG. 2A is an exploded isometric view of a first exemplary evaporatorembodiment in accordance with the present invention;

FIG. 2B is an isometric view illustrating a wicking structure disposedwithin the base of the evaporator shown in FIG. 2A;

FIG. 2C is an isometric view of the embodiment of FIG. 2A upon assembly;

FIG. 3A is an exploded isometric view of a second exemplary evaporatorembodiment in accordance with the present invention;

FIG. 3B is an isometric view of the embodiment of FIG. 3A upon assembly;

FIG. 4A is a topside exploded isometric view of a first exemplaryslim-line condenser in accordance with the present invention;

FIG. 4B is an underside isometric exploded view of the condenser of FIG.4A;

FIG. 4C is an isometric view of the condenser of FIG. 4A upon assembly;

FIG. 4D is a plan view of the condenser of FIG. 4A that illustrates theflow path the working fluid takes as it passes through the condenser;

FIG. 5A is an exploded isometric view of a cooling device that includesthe condenser of FIG. 4A;

FIG. 5B is an isometric view of the cooling device of FIG. 5A uponassembly;

FIG. 6A is an isometric view of a second exemplary condenser inaccordance with the present invention;

FIG. 6B is an isometric cut-away view of the condenser of FIG. 6A;

FIG. 7A is an elevational end view of a third exemplary condenser inaccordance with the invention;

FIG. 7B is a plan view of the condenser of FIG. 7A;

FIG. 8 is an isometric view of a 1U chassis computer server in which afirst exemplary CPL cooling system embodiment of the present inventionis implemented;

FIG. 9 is an elevational view of the components of the CPL coolingsystem of FIG. 8;

FIG. 10 is an isometric view of a 1U chassis in which a second exemplaryCPL cooling system embodiment of the present invention is implemented;

FIG. 11 is an isometric view of a 1U chassis computer server in which athird exemplary CPL cooling system embodiment of the present inventionis implemented; and

FIG. 12 is an elevational view of the components of the CPL coolingsystem of FIG. 11.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

In the following description, numerous specific details are provided toprovide a thorough understanding of embodiments of the invention. Oneskilled in the relevant art will recognize, however, that the inventioncan be practiced without one or more of the specific details, or withother methods, components, etc. In other instances, well-knownstructures or operations are not shown or described in detail to avoidobscuring aspects of various embodiments of the invention.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the present invention. Thus, theappearances of the phrases “in one embodiment” or “in an embodiment” invarious places throughout this specification are not necessarily allreferring to the same embodiment. Furthermore, the particular features,structures, or characteristics may be combined in any suitable manner inone or more embodiments.

The present invention concerns a modular capillary pump loop (CPL)thermal cooling system that transfers heat from high-power circuitcomponents (e.g., microprocessors) disposed within a computer chassis toother locations within or external to the chassis, where the heat can bemore easily removed through condensing the CPL's working fluid. A CPL isa two-phase thermal management system that uses capillary forces to pumpthe working fluid from a heat acquisition device(s) (e.g., anevaporator) to a heat radiation device(s) (e.g., a condenser).

A typical CPL system is shown in FIG. 1. The CPL system includes anevaporator 10 and a condenser 12 connected via a vapor transport line 14and a liquid transport line 16. Evaporator 10 includes a wick structure20 disposed in a lower portion thereof, and is adapter to be coupled toa heat source 22, such as a microprocessor. In the embodiment shown,condenser 12 also functions as a two-phase liquid reservoir. Optionally,the system may include one or more liquid reservoirs apart from thecondenser. In other embodiments, the CPL system may also include one ormore liquid subcooler and/or isolators (not shown).

The CPL system operates in the following manner. Heat produced by heatsource 22 is received by the lower portion of evaporator 10, causingliquid held in a meniscus layer 24 at the top of wick structure 20 toevaporate into vapor 26. Vapor 26 is then caused to be transported viavapor transport line 14 to condenser 12 by means of atemperature-induced pressure gradient caused by a difference in thetemperature of the vapor in vaporizer 10 (high temperature) and thevapor in condenser 12 (lower temperature). Condenser 12 is maintained ata lower temperature by means of heat removal 28, which typically will byaccomplished through a combination of forced convection and/or heattransfer fins on the condenser. Accordingly, upon entering thelower-temperature condenser 12, vapor 26 condenses into condensate 30,comprising liquid drops that are formed on the ceiling and walls of thecondenser. As the condensate drops increase in size, their weightovercomes their surface tension, causing them to eventually fall intoliquid 32, which is contained at the bottom portion of condenser 12.Liquid 32 is then transported via liquid transport line 16 back toevaporator 10 to complete the cycle.

As is name suggests, a capillary pumped loop uses a capillary action tocause the liquid in the loop to be pumped. This is accomplished throughthe use of wicking structure 20. More specifically, a pressuredifferential is produced at the liquid-vapor meniscus boundary at top ofthe wicking structure. This pressure differential causes liquid 32 to bedrawing into wicking structure 20 as liquid is evaporated at the top ofthe wicking structure into vapor 26.

As liquid 32 is evaporated into vapor 26, heat is transferred from heatsource 22 at a rate that is based on the latent heat of vaporization ofthe fluid and the flow rate of the liquid through the loop. In oneembodiment, the liquid is water, which has a latent heat of vaporizationof 2258-2432 kJ/kg (970-1052 Btu/lbm). In a similar manner, as the vaporis condensed back to a liquid in condenser 12, heat is removed as afunction of the latent heat of vaporization of the fluid and the flowrate of the fluid through the loop.

According to one aspect of the invention, CPL embodiments are providedthat are modular, wherein multiple components may be used in the CPLloop, as appropriate, and various system components may be replaced byother system components that provide similar functionality. For example,the module CPL cooling systems provided by the invention may includevarious types of evaporators, condensers, reservoirs and transport lineconfigurations, and may be configured operate in single andmulti-processor computer systems.

An evaporator 40 according to a first exemplary evaporator embodiment ofthe invention is shown in FIGS. 2A-C. Evaporator 40 comprises a two-partshell configuration including a base 42 having a cavity 44 covered by atop cover 46 so as to form a sealed volume. Liquid is provided to theevaporator via an liquid inlet port 48, while vapor exits the evaporatorvia a vapor outlet port 50. The evaporator further includes a wickingstructure 52 disposed in a lower portion of cavity 44. In oneembodiment, wicking structure 52 comprises a volume of a sintered metalpowder, which provides a high capillary pumping capability. In lowerpower applications (i.e., applications that can use relatively lowliquid flow rates), wicking structure 52 may comprise a wire mesh. Whena sintered metal power is used, the lower portion of cavity 44 may befilled with the powder and then heated, producing a sintered metalpowder layer that is integral to base 42, as shown in FIG. 2B.

Preferably, the materials used for the components in the evaporator, aswell as other components in the CPL system, should be selected to becompatible with the working fluid used in the system. In one embodiment,the working fluid comprises water. Accordingly, the components of theevaporator and other system components should be made of materials thatwill no rust or otherwise deteriorate in the presence of water. Forexample, in one embodiment, each of base 44 and top cover 46 are made ofcopper, and wicking structure 52 comprises a sintered copper powder.

Another consideration is that various embodiments discussed herein maybe operated under sub-atmospheric (i.e., vacuum) conditions. Byoperating under reduced pressures, the boiling and condensation pointsof the liquid are lowered. This allows the surface of the component(s)being cooled to operate at a lower temperature. For instance, if waterunder atmospheric pressure is to be used, the temperature at the surfaceof the component being cooled, such as a microprocessor, would have tobe (somewhat significantly) above the boiling point of water (212° F.).Furthermore, since heat transfer is driven by the temperaturedifferential between interfaces, it is desired that the temperature ofbase 42, which will be in thermal contact with the component beingcooled, be as low as possible.

In order to provide a sub-atmospheric loop, it is necessary that thevarious operating volumes in the loop be sealed. Therefore, top cover 46need to be secured to a peripheral portion of base 44 so as to form ahermetic (or near-hermetic) seal. As depicted by FIGS. 2A-C, top cover46 may be secured to base 42 using a plurality of fasteners 54. In oneembodiment, a gasket may be used to ensure a hermetic seal (not shown).In another embodiment, the top cover and base may be secured using ahermetic braze or weld.

In addition to sealing considerations, structural considerations alsoneed to be made when designing sub-atmospheric CPL systems. For example,either or both of base 44 and top cover 46 may include a plurality ofposts 56 that are used to ensure that the sealed volume does notcollapse when the pressure inside of the volume is reduced. Posts 56also assist in the vaporization of the working fluid by conducting heatfrom the heat source.

A second exemplary evaporator 60 embodiment is shown in FIGS. 3A-B.Evaporator 60 includes a base 62 in which a cavity 64 is defined, awicking structure 66, a top cover 68, a liquid inlet port 70, and avapor outlet port 72. As depicted, top cover 68 includes a plurality ofdimples to strengthen the top cover and prevent it from collapsing whena vacuum is applied to evaporator 60. As before, top cover 68 may besecured to base 62 to form a sealed volume using a plurality offasteners (not shown) or a hermetic braze or weld.

In general, each of embodiments 40 and 60 functions in a manner similarto evaporator 10 discussed above with reference to FIG. 1. Thecomponents of embodiment 40 will typically be formed using machiningoperations, stamping operations, and/or casting operations. Thecomponents of embodiment 60 may be formed using an appropriate sheetmetal using stamping operations. Ideally, materials having good thermalconduction properties should be used, such as copper alloys.

Details of a first exemplary condenser embodiment 80 are shown in FIGS.4A-5D. Condenser 80 includes a channeled base member 82 over which acover plate 84 is disposed upon assembly. Cover plate 84 includes avapor inlet port 86, a pair of liquid outlet ports 88L and 88R, and acharging port 90. As shown in FIG. 4B, in one embodiment cover plate 84includes a plurality of posts 92 that are used to strengthen the coverplate and prevent it from collapsing when condenser 80 is used insub-atmospheric CPL systems. The posts also act as nucleation sites forcondensate formation, by effectively conducting heat out of thecondenser, and provide effective entrainment traps for the vapor flowingpast them. Cover plate 84 further includes a hole 94 and a plurality offastener clearance holes 96.

As shown in FIGS. 4A and 4D, channeled base member 82 includes aplurality walls that are configured to guide fluid condensed in acentral condensing region of condenser 80 out through liquid outletports 88L and 88R. These walls include an external wall 98, a left innerwall 100L, a right inner wall 100R, a left capillary wall 102L, a rightcapillary wall 102R, a flow diverting wall 104, and a through-hole wall106. The external wall and left and right capillary walls 102L and 102Rform respective thin capillary channels 108L and 108R. Channeled basemember 82 further includes a through-hole 110 and a plurality of bosses112 configured in a hole pattern adapted to align with respectivefastener holes 96 in cover plate 84; each boss includes a clearance hole113 through which a fastener shank passes upon assembly of the condenser(fasteners not shown).

As shown in FIG. 4D, condenser 80 operates in the following manner.Vapor 26 enters the condenser via vapor inlet port 86. The vapor is thencondensed on the underside of cover plate 84 and various walls of thecondenser in the central condensing region creating liquid 32. Liquid 32is then drawn out of the condenser through liquid outlet ports 88L and88R by means of a combination of a lower pressure at the external sideof the liquid outlet ports (relative to the pressure inside thecondenser) and the capillary action created by capillary channels 108Land 108R.

It is noted that in one embodiment there are a pair of areas 114L and114R in which neither vapor or liquid is present. These areas are usedto thermally isolate the vapor/liquid mixture disposed in the center ofthe condenser from the liquid in capillary channels 108L and 108R.

Charge port 90 is used to “charge” condenser 80 with the working fluidin the CPL systems that use the condenser. It is envisioned that thecondenser will be charged by holding the condenser vertical (i.e., theconfiguration shown in FIG. 4D) and filling the lower portion of thecondenser with the working fluid. The symmetric configuration of thecondenser should ensure that both capillary channels are properlycharged with the working fluid. The working fluid will flowsymmetrically out of the liquid outlet ports into the liquid transportline(s) and saturate the wicking structure(s) in the CPL systemevaporators, thereby providing for proper charging and priming of theCPL system.

The central condensing portion of condenser 80 also serves as areservoir when used in a CPL system. This enables steady temperature andpressure conditions to be maintained in the CPL, and is also useful toaccommodate power surges.

In order to obtain enhanced performance, condenser 80 may be coupled toa heat dissipation device, such as a heatsink. Preferably, heat removalvia the heat sink will be enhanced by causing air to flow across theheatsink. An exemplary heat removal device 120 that incorporatescondenser 80 and provides the foregoing functionality is shown in FIGS.5A and 5B. Heat removal device 120 includes a heatsink 122, a motor 124,and an annular centrifugal fan rotor assembly 126 that includes aplurality of fan blades that are radially disposed about a center of therotor. In one embodiment, heatsink 122 includes an array of pins 128connected to a base plate 130. The heatsink is coupled to cover plate 84by means of a plurality of fasteners (not shown), wherein the head ofthe fasteners are disposed within clearances 132 defined in the array ofpins. Motor 124 is secured to heatsink 122 with three fasteners (notshown) that are threaded into three respective threaded standoffs 136.Annular centrifugal fan rotor assembly 126 is then secured to motor 124at the motor's shaft 138.

Heat removal device operates in the following manner. Heat istransferred from condenser 80 via cover plate 84 to base 130 of heatsink 122. The heat then flows to the array of pins in the heat sink. Asmotor 124 turns centrifugal fan blade assembly 126, air is caused toflow past the array of pins, thereby cooling them. The heated air isthen exhausted outward from the fan blades. If desired, the exhaustedair may be directed toward a desired outlet via appropriate ducting.

A second exemplary condenser embodiment 140 is shown in FIGS. 6A and 6B.Condenser 140 includes a body 142 including a cavity 144 into whichvapor enters through a vapor inlet port 146 and out of which liquidexits through a liquid outlet port 148. In one embodiment, a heatsink150 including a plurality of fins 151 is integrated into body 142.Optionally, a heatsink may be attached to body 142 as a separate part. Acover 152, including an integrated heatsink 154 comprising a pluralityof fins 155 is disposed over cavity 144 to form an enclosed volume uponassembly of the cover to body 142. Body 142 further includes a pluralityof posts 156 for structural purposes in sub-atmospheric embodiments andnucleation enhancement.

As vapor 26 enters cavity 144 through vapor inlet port 146, it condensesinto droplets on the walls in the upper portion of the cavity;eventually the droplets fall to the lower portion of the cavity to formliquid 32, which exits the cavity through liquid outlet port 148. Thelarge surface area of the fins of heatsinks 150 and 154 assist inkeeping condenser 140 at a low operating temperature, increasing theefficiency of the condensing process.

A third exemplary condenser embodiment 160 is shown in FIGS. 7A and 7B.Condenser 160 comprises a single loop of tubing 162 having a helicalconfiguration and a plurality of circular fins 164 axially disposedabout the tubing. Condenser 160 further includes a vapor inlet port 166and a liquid outlet port 168. During operation, vapor 26 enters vaporinlet port 166 and begins to condense on the inner walls of tubing 162.As the vapor condenses, it is converted to droplets that eventually rolldown the tubing walls and collect in the lower elevation portion of thetubing (i.e., the right-hand portion of the tubing in FIG. 7A). Thecondensed working fluid then exits the condenser through liquid outletport 168.

A first exemplary CPL system embodiment 180 in accordance with thepresent invention is shown in FIGS. 8 and 9. As shown in the FIG. 8, CPLsystem 180 may be implemented in a computer server housed in a 1Uchassis 182. The computer system includes various computer circuitry andprinted circuit boards (PCBs), including a pair of processors 184A and184B coupled to modular processor boards. It is noted that several ofthe computer server's components, such as disk drives PCBs, electricalconnectors, main board, etc. have been removed from the configurationshown in FIG. 8 for clarity. CPL system 180 includes a pair ofevaporators 60A and 60B mounted to respective processors 184 such thatthe top surface of each processor is thermally coupled to a base 62 ofthe evaporator the processor is mounted to. In optional configurations,various heat transfer compounds may be used to enhance the thermalcoupling between the evaporator base and the processor.

The vapor outlet ports 72 of the evaporators are commonly connected to atee connection 186 through a pair of flexible vapor transport lineportions 187 and 188. The common port of the tee connection is connectedto a flexible vapor transport line 190, which has an outlet side that isconnected to a vapor inlet port 86 of a condenser 80. Condenser 80 ispart of a heat removal device 120, as described above with reference toFIGS. 5A and 5B. The liquid outlet ports 88L and 88R of condenser 80 areconnected to first ends of respective liquid transport lines 192 and194. The other end of liquid transport line 192 is connected to theliquid inlet port 70 of evaporator 60A, while the other end of liquidtransport line 194 is connected to the liquid inlet port 70 ofevaporator 60B.

An elevation view of CPL system 180 is shown in FIG. 9. It is importantto recognize that the design of CPL systems in accordance with theinvention must consider the elevational configuration of the componentused in the system. Generally, rack-mounted servers, such as 1U and 2Uservers, are configured as a plurality of servers stacked horizontally.As shown in FIG. 9, the condenser is located such that it has anelevation that is similar to that of the evaporator and transport lines.This reduces system pressure losses, increasing the efficiency of thesystem.

A second CPL system embodiment 200 is shown FIG. 10. Many of thecomponents in the right-hand portion of the 1U server are substantiallythe same as described above with reference to FIG. 8; accordingly, thesecomponents share the same reference numerals in both of FIGS. 8 and 10.CPL system 200 includes three condensers 140A, 140B, and 140C havingconfigurations similar to that of condenser 140 discussed above withreference to FIGS. 6A and 6B. As with CPL system 180, vapor 26 exitsevaporators 60A and 60B via vapor outlet ports 72, flowing into tee 186via vapor transport lines 187 and 188. Tee 186 is connected to one endof a flexible vapor transport line 202. The other end of the vaportransport line is connected to a manifold 204, which divides the vaporinto three portions. The output branches of manifold 204 are coupled torespective vapor inlet ports 146 of condensers 140A, 140B, and 140C. Asimilarly configured manifold (not shown) connects the liquid outletports 148 of the condensers to one end of a flexible liquid transportline 206, while the other end of the liquid transport line is connectedto a tee 208. The branches of tee 208 are connected ends of respectiveliquid transport lines 210 and 212, while the ends of the liquidtransport lines are connected to respective liquid inlet ports 70 ofevaporators 60A and 60B.

CPL system 200 further includes a plurality of muffin fans 214. Thesefans are used to draw air across the fins of the condensers, therebycooling the condensers and enhancing the heat removal capability of thesystem. Typically, muffin fans 214 will be located in an outer portionof the chassis.

A third exemplary CPL system embodiment 220 is shown in FIGS. 11 and 12.Many of the components in the right-hand portion of FIG. 11 are similarto those used in CPL system 180 discussed above; these components sharethe same reference numbers in both FIGS. 8 and 11. As with CPL system180, vapor 26 exits evaporators 60A and 60B via vapor outlet ports 72,flowing into tee 186 via vapor transport lines 186 and 187. Tee 186 isconnected to one end of a flexible vapor transport line 222. The otherend of the vapor transport line is connected to a vapor inlet port 166of a condenser 160. A centrifugal fan 126 coupled to a motor 124 isdisposed within condenser 160 and is used to cause air to flow over fins164 to enhance the condensation function of the condenser when turned bythe motor.

The liquid outlet port 168 of the condenser is connected to an inletport 224 of a reservoir 226 via a liquid transport line 228. An outletport 229 of the reservoir is connected to a tee 230 via a liquidtransport line 232. The branches of tee 230 are connected to ends ofrespective liquid transport lines 234 and 236, while the ends of theliquid transport lines are connected to respective liquid inlet ports 70of evaporators 60A and 60B.

The present invention provides several advantages over the prior art.For example, large heatsinks are commonly used in the prior art forcooling microprocessors. These heatsinks are often heavy and may becaused to vibrate in forced convention environments. Furthermore, inenvironments in which the chassis is caused to vibrate, such asrack-mount configurations in which multiple servers are mounted, thevibration and shocks induced to the chassis coupled with the weight ofthe heatsinks may damage the processor leads. By using flexibletransport lines, vibration coupling between components may bedramatically reduced. Furthermore, since the CPL systems do not uselarge heatsinks but rather only have the evaporator component attachedto the processors, the foregoing vibration problem may be reduced.Additionally, CPL systems enable the heat to be moved to locations incomputer system chassis that are better configured for heat removal. Asa result, higher density server configurations can be sufficientlycooled for high-reliability operations. The present invention alsoavoids some of the drawbacks of heat pipe systems. Notably, since CPLsystems have a lesser amount of wicking structure, the pressure lossesseen by the working fluid is reduced, thereby increasing heat capacityand maximum thermal transport distance.

Although the present invention has been described in connection with apreferred form of practicing it and modifications thereto, those ofordinary skill in the art will understand that many other modificationscan be made to the invention within the scope of the claims that follow.Accordingly, it is not intended that the scope of the invention in anyway be limited by the above description, but instead be determinedentirely by reference to the claims that follow.

1. A thin-profile condenser, comprising: a cover plate; a channeled basemember having an external wall extending around a periphery thereof towhich a cover plate is secured so as to define a sealed cavity; a pairof capillary walls, each capillary wall including a portion disposedsubstantially adjacent to a portion of the external wall so as to definea pair of capillary channels, said capillary walls dividing the sealedcavity into a condensing region and the capillary channels; a pair ofinner walls, each internal wall coupled to a corresponding one of thepair of capillary walls to create a thermal isolation area between eachinner wall and its corresponding capillary wall, wherein there isneither liquid nor vapor in the thermal isolation areas; a vapor inletport to receive a working fluid in a vapor state operatively coupled tothe sealed cavity; and a first liquid output port from which the workingfluid exits the condenser, operatively coupled to an outlet end of eachcapillary channel.
 2. The thin-profile condenser of claim 1, furthercomprising a charge port operatively coupled to the condenser to enablethe condenser to be charged with the working fluid.
 3. The thin-profilecondenser of claim 1, further comprising a hole extending through thecondensing region.
 4. The thin-profile condenser of claim 1, whereinsaid at least one internal wall includes portions that are configuredsymmetrically so as to form a centrally-disposed condensing regionconnected to a first capillary channel disposed on a first side of thecondensing region and a second capillary channel disposed on a secondside of the condensing region opposite of the first side.
 5. Thethin-profile condenser of claim 1, further comprising a second liquidoutlet port operatively coupled to an outlet end of the second capillarychannel.
 6. The thin-profile condenser of claim 1, further comprising aplurality of posts disposed within the condensing region extendingbetween the channeled base member and the cover plate.
 7. Thethin-profile condenser of claim 1, further comprising a heatsinkthermally coupled to the cover plate.
 8. The thin-profile condenser ofclaim 7, wherein the heatsink comprises a base plate having a pluralityof pins extending upward therefrom.
 9. The thin-profile condenser ofclaim 7, further comprising a centrifugal fan including an annular fanrotor having a plurality of fan blades disposed around a periphery ofthe heatsink so as to draw air across the heatsink when rotated.